As a rule, because of mass production, molds for concrete series-produced finished railroad ties are made to be very rigid and durable. This applies particularly to ties produced in succession in a prestressing bed. In this case, there are very high demands for a particularly accurate measurement of the positions of the tie components. Therefore, the construction elements are fastened in bores of the mold which have to be positioned extremely accurately.
In the case of railway ties, the construction components--anchor screws or sleeves for the fastening screws of the track cross ties--are located on the upper side of the cross tie. The upper side of the cross tie lies in the mold, on the mold bottom, that is the cross tie is molded upside down. Thus, the bottom plate serves as a pattern for the insertion of the construction components.
In large series, a hole template is often used. The pattern which has to be produced for each type of tie only slightly influences the cost of the individual tie. But in the case of smaller production series of a certain cross-tie type, the costs related to the bottom plate serving as a pattern for the construction components can make the process uneconomical.
Particularly complicated is the making of the holes in the patterns for the switch cross ties. In normal track ties, the rail axes cross the switch ties perpendicularly. The construction components for the fastening of the rail to the switch tie and correspondingly the bores fixing them to the bottom plate of the mold are located on the median axis at a spacing determined by the gauge of the system.
Things are different in the case of switch cross ties. Here as a rule, the rail axes cross the switch tie axes at various normally non-right angles. Up to now, for fastening of rail tracks which do not cross the ties at right angles slabs were used which had their bores located on the axis and which required construction components arranged in numerous axes scattered over the surface of the switch ties for the fastening screws of the slabs and corresponding bores for the fastening of the construction components in the bottom plate of the mold. A mold for switch cross ties made of concrete is known from German patent 3,440,247. This mold has a bottom plate made of steel which is accurately fitted between side walls. Nonetheless with it the production of new bottom plates with holes in different locations and their insertion is expensive.